Comprehending Climate Complexities

The Global and European Calculators are tools that can be used for both exploring the future of our climate and working out what can be done about it, helping us better understand climate complexities.
This article appeared in Vol. 17, No. 1 - 2020


Comprehending Climate Complexities

The Global Calculator is an open access, publicly available decision support tool that was developed to assist decision makers, particularly the national negotiators, in the lead-up to the Paris Climate Conference that was held in December 2015. The Global Calculator was based on an existing UK 2050 Climate Calculator. This calculator, developed by the UK government (DECC, Department for Energy and Climate Change) was designed to provide policy makers with the chance to explore the full range of pathways available for the UK to transition to a low carbon economy; pathways that were compatible with achieving EU and global temperature targets for 2100.

  • The Global Calculator summary interface. The lower half shows the selectable options such as lifestyle, technology, fuel, foods and demographics while the panel above shows the impacts of the selected scenario on energy supply and demand (top left); greenhouse gas emissions per year (centre) and cumulative CO2 emissions and global mean temperature ranges (top right). Source:

A unique aspect of the Calculators is that they are not designed to provide optimised outcomes; instead, they put the user in control of exploring a broad range of options, varying from minimal adjustment through to extremely ambitious climate change mitigation. The user directly and immediately sees the impacts of choices made when selecting specific technological and behavioural options that span across lifestyles, technology and fuels, land and food choices and population sectors.

The Global and European Calculators: Key Principles for Development

The calculators are targeted at decision support and enabling the building of transition pathways to 2050. They must, therefore, encompass a very broad range of technological and behavioural innovation options. In addition, immediacy of response is also important if the Calculators are to be relevant to policy makers, particularly when entering negotiations. The user must also trust that the impacts calculated from the choices made are a robust representation of the real-world outcomes projected into the future.

In order to achieve this level of robustness and trust the development of the Calculators is guided by three primary principles:

  • Openness: the calculators are built on an Excel-based tool which is fully published and available free online; 
  • Collaboration: they have been designed by a global team using input from hundreds of experts; 
  • Simplicity, with the aim of modelling the world in the simplest form possible, whilst including all energy sources and uses, emissions and a full range of future scenarios. 

A fourth principle of co-design has also been adopted to ensure that the Calculators remain relevant to the users and meet their needs. 

Forty ‘levers’ enable the user to vary the way we might live in the future, including the amount and types of energy we might use, how we travel and even our diet, including calories consumed, and quantity and type of meat. Each lever can be set to one of four levels of ambition for climate mitigation which relate to the full range of what is possible to achieve for that specific sector, technology and/or behaviour.

  • The user of the Global Calculator can adjust predicted outcomes by selecting the level of change applied for various behavioural and technical factors. Source:

The user is also able to select a pre-defined pathway from a list of example pathways, including scenarios such as ‘distributed effort’, ‘consumer reluctance’ and ‘low action on forests’. 

Exploring the Global Calculator

The main goal of the Global Calculator was to answer the question: is it physically possible to meet our climate targets and ensure everyone has good living standards by 2050? The calculator demonstrates that there are very many different pathways available that allow us to achieve no more than a 2°C rise in global mean temperatures by 2100, and the team have published four plausible exemplar pathways which would ensure good lifestyles as well as explore the main uncertainties surrounding technology, fuels and land use. The key points these pathways show are:

  1. It is possible for 10 billion people (the estimated global population by 2050) to eat well, travel more and live comfortably whilst reducing emissions by 50%.
  2. To do this, technology and the fuels we use need to be transformed. CO2 emitted per unit of electricity globally needs to fall by at least 90% by 2050, while electric or zero-carbon sources for heating homes needs to increase from 5 to 25–50%.
  3. Land resources; we need to be smarter about land use. Specifically, forest protection and expansion globally needs to increase by 5–15% due to the ecosystem service of being a carbon sink.

Perhaps the most controversial and important novel outcome from the Global Calculator is that we can no longer focus exclusively on emissions reduction in the energy sector. Without achieving a significant expansion of carbon sinks on the land and reductions in emissions from the food sector, and in spite of any significant reductions we might see in energy sector emissions, the Calculator found that meeting even the 2°C, never mind the 1.5°C target, will not be possible. To demonstrate this, the sensitivity of global climate mitigation pathways to the food production and dietary levers is shown in the graphs to the right.

  • Global Greenhouse gas emissions trajectory per year (GtCO2e), all using an initial 4°C global emissions pathway (IEA 4DS) (a) with dietary levers set to ‘level 1’ – i.e. minimal mitigation ambition, equivalent to a global average diet in 2050 that is equivalent to the current European average diet; (b) with dietary levers set to ‘level 2’, in which the global average calorie consumption increases to a level similar to projections by the UN’s Food and Agricultural Organisation (Alexandratos and Bruinsma, 2012, adjusted to exclude food losses) of 2,330 kcal per person per day; and (c) with dietary levers set to ‘level 4’ – an extreme mitigation ambition, equivalent to a global average diet similar to the current Indian diet. Source:

The Global Calculator: An Invaluable Open Source Tool for Comprehending Climate

With no silver-bullet solution to the climate crisis, the Global Calculator has been a predecessor for more regionally specific 2050 calculators, including the EU 2050 calculator (EUCalc). The EUCalc is an interdisciplinary, collaborative model of intermediate complexity. Unlike the Global Calculator, which represents a closed system, the EUCalc considers transboundary relationships within the EU and Switzerland and between the EU and the rest of the world.

Tools such as the Global Calculator and the EUCalc project provide policy makers, decision makers and students with in silico models to assess the impacts, trade-offs and applications of the potential choices available in real-time. In a climate where it is becoming even more urgent to make the right decisions now and to act on them as quickly as possible, having an open source tool which makes comprehending the complexities of the climate crisis a little bit easier is invaluable.

Further Reading on Climate

Recent Advances in Climate Change Research: Part I - Blackbody Radiation and Milankovic Cycles
Martin Landrø and Lasse Amundsen, NTNU / Bivrost Geo
Geoscience will probably play an important role in mitigating carbon dioxide emissions. In part one of this series, we discuss some history and physics behind the topic of climate change including the concepts behind blackbody radiation and Millankovic Cycles.
This article appeared in Vol. 16, No. 2 - 2019

Energy and Climate Change
Dr. Nick Riley
A review of Michael Stephenson's book titled: "Energy and Climate Change: An Introduction to Geological Controls, Interventions and Mitigations" published in 2018 by Elsevier.
This article appeared in Vol. 15, No. 6 - 2019


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